We are using energy all the time. Without energy, we would not be able to use our brains, or make our muscles move. Energy moves cars along the road, bakes a cake in the oven and lights our home.
Asleep, awake, eating, bathing, grooming, working or engaging in passionate pursuits, you need energy, which is supplied from your diet in the form of calories. Energy fuels your body’s internal functions, repairs, builds and maintains cells and body tissues, and supports the external activities that enable you to interact with the physical world. Water, your body’s most important nutrient, helps facilitate the chemical reactions that produce energy from food.
Basal Metabolism
Basal metabolic rate, or BMR, is the minimal amount of energy needed to keep your body functioning and alive while at rest. BMR uses about 60 to 65 percent of daily energy stores, according to the University of Maryland School of Medicine. In the resting state, energy supports circulation, respiration, digestion, excretion and other functions performed by vital organs. Seven percent of your total energy supply keeps your body warm. Energy needs differ according to age, gender, body composition, health status, diet and activity level.
Body Composition
Body composition is one determinant of energy requirements. Muscle is the body’s most metabolic tissue, which means it requires more energy than other body tissues to maintain itself. Because they are naturally more muscular, men need more energy – calories – than women do. Children and young adults undergoing developmental changes in height, weight and body composition have greater energy needs. Energy requirements change as people age, because muscle tissue atrophies, causing a reduction in basal energy metabolism, according to the Colorado State University Extension website.
Digestion and Absorption
Digestion and absorption of the nutrients in food use 5 to 10 percent of your daily energy stores to produce more energy, according to the University of Maryland School of Medicine. Diet composition also determines energy requirements for food metabolism. Carbohydrates, protein and fats are digested at different rates. Digesting protein uses the most energy, or about 20 to 30 percent of the calories in the food. Carbohydrates use 5 to 10 percent of calories and fat uses 0 to 3 percent.